甲状旁腺激素的促骨形成作用研究

甲状旁腺素(PTH)在体内最为重要的作用就是调节钙、磷代谢,近年来的研究证明,PTH在骨的代谢过程中也有着极其重要的作用.目前,PTH及其片段已成为重要的骨形成促进剂,尤其是PTH1-34已由美国礼来(lilly)公司开发为治疗骨质疏松症的药物特立帕肽(teriparatide),它是目前临床应用效果最好的的促进骨合成代谢的药物.本文就PTH的结构、作用机制及其对骨的作用和特里帕肽的研究进展作一综述.     

Xanthophyllomyces dendrorhous for the industrial production of astaxanthin

Astaxanthin is a red xanthophyll (oxygenated carotenoid) with large importance in the aquaculture, pharmaceutical, and food industries. The green alga Haematococcus pluvialis and the heterobasidiomycetous yeast Xanthophyllomyces dendrorhous are currently known as the main microorganisms useful for astaxanthin production at the industrial scale. The improvement of astaxanthin titer by microbial fermentation is a requirement to be competitive with the synthetic manufacture by chemical procedures, which at present is the major source in the market. In this review, we show how the isolation of new strains of X. dendrorhous from the environment, the selection of mutants by the classical methods of random mutation and screening, and the rational metabolic engineering, have provided improved strains with higher astaxanthin productivity. To reduce production costs and enhance competitiveness from an industrial point of view, low-cost raw materials from industrial and agricultural origin have been adopted to get the maximal astaxanthin productivity. Finally, fermentation parameters have been studied in depth, both at flask and fermenter scales, to get maximal astaxanthin titers of 4.7 mg/g dry cell matter (420 mg/l) when X. dendrorhous was fermented under continuous white light. The industrial scale-up of this biotechnological process will provide a cost-effective method, alternative to synthetic astaxanthin, for the commercial exploitation of the expensive astaxanthin (about $2,500 per kilogram of pure astaxanthin).     

Editor's choice: AnABlast: a new in silico strategy for the genome-wide search of novel genes and fossil regions

Genome annotation, assisted by computer programs, is one of the great advances in modern biology. Nevertheless, the in silico identification of small and complex coding sequences is still challenging. We observed that amino acid sequences inferred from coding—but rarely from non-coding—DNA sequences accumulated alignments in low-stringency BLAST searches, suggesting that this alignments accumulation could be used to highlight coding regions in sequenced DNA. To investigate this possibility, we developed a computer program (AnABlast) that generates profiles of accumulated alignments in query amino acid sequences using a low-stringency BLAST strategy. To validate this approach, all six-frame translations of DNA sequences between every two annotated exons of the fission yeast genome were analysed with AnABlast. AnABlast-generated profiles identified three new copies of known genes, and four new genes supported by experimental evidence. New pseudogenes, ancestral carboxyl- and amino-terminal subtractions, complex gene rearrangements, and ancient fragments of mitDNA and of bacterial origin, were also inferred. Thus, this novel in silico approach provides a powerful tool to uncover new genes, as well as fossil-coding sequences, thus providing insight into the evolutionary history of annotated genomes.     

2001-2019年中国自然保护区生态环境质量时空变化特征及其驱动力

自然保护区对维护生物多样性,改善生态环境质量具有重要作用。然而,我国自然保护区生态环境质量变化及其对自然因素与人类活动的响应规律还不清晰,理解这些规律对我国的生态文明建设以及生物多样性的保护具有重要意义。基于2001—2019年中国历史高分辨率生态环境质量数据CHEQ数据集以及自然因素,利用Theil-Sen Median趋势分析、Mann-Kendall检验以及多元回归残差分析等方法,探究了2001—2019年中国自然保护区的生态环境质量时空变化特征及其对自然因素与人类活动驱动因素的响应。结果表明：(1)我国自然保护区的CHEQ指数呈现多阶段波动变化,总体呈小幅度下降趋势,平均趋势率为-0.54×10^-3/a;在空间上,中国自然保护区CHEQ变化趋势值呈“南高北低,东高西低”的分布格局;(2)自然因素与人类活动的共同作用是我国自然保护区生态环境质量恶化的主要原因,且恶化区域主要分布在自然保护区的实验区和缓冲区。其中自然因素对我国自然保护区生态环境质量变化的影响在-3×10^-3/a—0/a之间,人类活动的影响在-1×10^-3     

Bacillus subtilis RecA and its accessory factors,RecF, RecO,RecR and RecX,are required for spore resistance to DNA double-strand break

Bacillus subtilis RecA is important for spore resistance to DNA damage, even though spores contain a single non-replicating genome. We report that inactivation of RecA or its accessory factors, RecF, RecO, RecR and RecX, drastically reduce survival of mature dormant spores to ultrahigh vacuum desiccation and ionizing radiation that induce single strand (ss) DNA nicks and double-strand breaks (DSBs). The presence of non-cleavable LexA renders spores less sensitive to DSBs, and spores impaired in DSB recognition or end-processing show sensitivities to X-rays similar to wild-type. In vitro RecA cannot compete with SsbA for nucleation onto ssDNA in the presence of ATP. RecO is sufficient, at least in vitro, to overcome SsbA inhibition and stimulate RecA polymerization on SsbA-coated ssDNA. In the presence of SsbA, RecA slightly affects DNA replication in vitro, but addition of RecO facilitates RecA-mediated inhibition of DNA synthesis. We propose that repairing of the DNA lesions generates a replication stress to germinating spores, and the RecA·ssDNA filament might act by preventing potentially dangerous forms of DNA repair occurring during replication. RecA might stabilize a stalled fork or prevent or promote dissolution of reversed forks rather than its cleavage that should require end-processing.     

Amplified detection of nucleic acid by G-quadruplex based hybridization chain reaction

A protein-free, isothermal, self-amplified nucleic acid sensing system which was a G-quadruplex integrated hybridization chain reaction (GQ-HCR) system was developed. The G-quadruplex was closed two-thirds in the loop and one-third in the stem of one of the GQ-HCR hairpin probes. In the absence of the target molecule, the GQ-HCR probes stayed as inactive meta-stable hairpin structures and the G-quadruplex was inert. Reversely, the GQ-HCR probes could be cross-opened to start a hybridization chain reaction and the closed G-quadruplex could be released to be free when the GQ-HCR probes came across the target molecule. The GQ-HCR nucleic acid sensing system could detect as low as 7.5nM ssDNA or RNA by the colorimetric method and 4nM ssDNA by the fluorometric method. Less than 10 copies of dsDNA template could also be detected when PCR was combined with the GQ-HCR system (PCR+GQ-HCR). Because of these advantages, the GQ-HCR system was also studied for application in visual chip detection to obtain a satisfactory repeatable and specific result.     

细叶卷柏提取物的体外抗肿瘤活性

利用MTT法检测细叶卷柏乙酸乙酯和正丁醇提取物对HeLa细胞生长的抑制作用,利用流式细胞术(FCM)比较不同提取物对细胞凋亡的影响。结果显示:细叶卷柏的乙酸乙酯和正丁醇部位抑制细胞生长和诱导细胞凋亡作用均有明显的剂量依赖性。乙酸乙酯部位的IC50值为1.927μg/mL,正丁醇部位的IC50值为24.600μg/mL。因此,细叶卷柏乙酸乙酯部位的体外抗肿瘤活性相对较强,其次是其正丁醇部位,水提部位相对较弱。细叶卷柏是一种潜在的抗肿瘤药用植物。     

水稻籽粒淀粉分支酶活性的遗传分析

用由247个株系组成的珍汕97B/密阳46重组自交系群体及其含207个分子标记的连锁图谱,在2002年和2003年分别测定亲本和重组自交系群体开花后10 d和20 d籽粒的淀粉分支酶的活性,检测到3个控制开花后10 d Q酶活性的主效应QTL(qnantitative trait loci),联合贡献率为10%,其中qQ10-6与环境发生显著的互作;分别检测到5对和2对染色体区间对开花后10 d、20 d Q酶活性的影响具有加性×加性上位性作用,其中开花后10 d的3对染色体区间具有显著的上位性×环境互作效应.由此可见,水稻籽粒Q酶活性相关基因的表达,受到环境因子的极大影响.